This paper canvasses aspects of my PhD research. The research project is premised on the hypothesis that Planning Law Decision Makers (PLDM) rely on tools such as social impact assessment, plans, maps, expert witnesses, planning legislation and related policy and regulatory instruments, to gain knowledge on social impacts for significant land use and development. It is positioned on the proposition that all of these, including PLDM themselves, are actors in the planning system. The study defines Planning Law Decision Makers (PLDM) as decision makers in the context of planning in the State of Victoria, Australia who make decisions on land use and development proposals. These include planning officers and managers at Councils, elected Councillors, members of the planning tribunal (Victorian Civil and Administrative Tribunal), Judges in superior courts who have jurisdiction to deal with planning matters and the State Minister for Planning. For the sake of this study, it also includes Planning Panel Members. Generally speaking, such panel members only make high level recommendations for planning matters and the Minister for Planning in this context, is the ultimate decision maker